Method of producing steel in basic open hearth furnaces



P. KHN

METHOD OF PRODUCNG STEEL IN BASIC OPEN HEARTH FURNACES 6 Sheets-Sheet 1 Filed March 10, 1935 /n venten:

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P. KUHN 1,991,685 METHOD OF PRODUGING STEEL IN BASIC OPEN HEARTH FURNACES Feb. 19, 1935.

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METHOD OF PRODUCING STEEL IN BASIC OPEN HEARTH FURNACES Feb. 19, 1935.

Filed March 10, 1953 6 Sheets-Sheet 6 /nventon' 73- KV;A

Patented `1"' eb. 19,- 1935 y `Latinas nmrnon orrnonociNG STEEL 1N Basic OPEN HEABTH FUBNACES raul Khn, Nieaemnelaen-sieg, Germany, signor to ilrm Vereinigte Stahlwerke Aktiengesellschaft, Dusseldorf, Germany Application March 10, 1933, Serial No. 660,32 In Germany March 10, 1932 '5 Claims. (Cl. 'l5-45) This invention relates to an improvement of the method forming the subject matter of patent application Serial No. 478,749, led August I29, 1930, which matured into Patent No. 1,979,629.

'Ihe patented method has to do with the production of steel of great toughness and low sens sitiveness with re t to cold brittleness, fatiguing and blue sho ess in an open hearth basic furnace, and consists in continually reducing, at high and uniform temperature and high basicity of the slag, manganese from the slag, continually increasing the manganese contents of the bath and reducing the FeO contents of the bath and slag while a special deoxidizing agent need not be added.

Further experiments have rendered the method applicable also to the production of low alloy steels in so far as the alloy elements are not added in the usual way as metals or iron alloys and placed in the furnace shortly before tapping or during tapping in the ladle, but are contained either as impurities already in the charge or as oxides in the charge or are introduced 'into the furnace shortly after melting down.A

-By applying the method described in Patent No. 1,979,629 (Ser. No. 478,749) it will then be possible, in addition to the manganese present in the charge, to reduce also alloy ,elements from the slag and to bring them into the bath whose 0 FeO ycontents will at the same time be reduced.

-Alloy elements whichV are added already to the charge or as ore in the furnace comprise, for example, chromium, vanadium, molybdenum, titar nium, tungsten, copper and nickel. Said elements may for instance be contained in the finished steel produced according to the invention up to the following amoimtsz' The nature of the method will be explained by two examples.

In the drawings are given graphical illustrations of the changes in the steel and slag constituents in the present smelting process for producing steel in open hearth furnaces, and

Figure 1 represents the first smelting course; one ingredient being chromium;

Figure 2 represents the second smelting course, when one ingredient ismolybdenum;

Figure 3, a similar diagram when one of the constituents is copper; l

Figure 4, a similar diagram when one of the ingredients is nickel;

Figure 5, a similar' diagram for vanadium and titanium; and

Figure 6 is a similar diagram `for tungsten.

The charge of the melt 1, whose smelting process is indicated by the change of the most important constituents of slag and bath in Fig. 1, contained, in addition to 2.18% manganese, 1.13% chromium from the scrap material. During introduction, the manganese contents of the bathamounted to 1.34% and the chromium contents, to 0.63%, so that part of the manganese and chromium contained in the charge had been transferred into the slag already during melting down. Manganese and chromium, owing to the addition of hammer scale, are passed-to a considerable extent as oxides over into the slag during the rst two hours as in the normal open hearth process, However, compared with the course of a normal open hearth melt, considerable variations will be noted in the manganese and chromium curve beginning with sample 5, owing to the addition of lime and an increase in temperature. Beginning with sample 6 or 7, chromium, in addition to manganese, is continually reduced from the slag and returned to the steel bath. Chromium contents at tapping amount to 0.4%, which constitutes a remarkable success compared with the yield of the normal open hearth process. y

Melt 2, whose smelting course is shown in Fig. 2,' received shortly after running. in an addition of 260 kilos of roasted molybdenite. Immediately after the addition, the molybdenum content of the steel amounted to 0.15%. After the addition of the lime in sample 3' the molybdenum content, parallel to the manganese curve in the steel, begins to increase continually, or, in other words, molybdenum is continually reduced from the slag. The molybdenum content of the finished steel was 0.45%.

In a similar manner it was possible to produce steel alloys containing besides manganese which may be present for instance up to 1.6% one or more of the following alloying elements:

Chromium up t0 1.6% Molybdenum up to 0.6% Copper up to 1.0% Nickel up to 2.0% Vanadium i upto 0.1% 'Titanium l up to 0.1% Tungsten s up to 1.8%

the slag. The arrows at the top on the left hand side of the figures indicate the times at which an addition of ore was made. The arrows at the top on the right hand side of the figures show the times at which an addition of lime was made. On the lower part of the figures the two arrows separate the oxidative part from the reductive one. The numbers 1 to 15, 1 to 10, 1 to 11, 1 to 9 respectively represent the numbers of the samples taken from the bath and the slag. The lower figures give the time in hours. The time at which the reduction period begins is represented by the numeral 0. After a reduction period of 3 hours (Fig. l) or 2 hours (Fig. 2-6) the steel was tapped.

Each of the figures of the drawings contain an upper part and a lower part. The upper part indicates the quantities of carbon and alloy metal contained in the steel bath and the lower part indicates the quantities of oxide contained in the slag in dependence of time. The vertical line extending through both parts near the time 0 divides both parts of the figures into a left and a right half. In the left half, there is so-called oxidation period and in the right half the reduction period. In the oxidation period the manganese is oxidized and therefore passes out of the bath over into the slag and vice versa in the reduction period manganese passes out of the slag over into the bath. Consequently, during the transition from the oxidation field to the reduction field, a bend in the manganese curve takes place. The same is the case with regard to chromium while the content of molybdenum, copper, nickel, vanadium, titanium and tungsten constantly increases. During the oxidation period ore is added at predetermined intervals. After the transition to theY reduction period, the adding of ore is discontinued and additions of lime are supplied.

What I claim and desire to secure by Letters Patent of the United States is:

1. A process of producing an alloyed steel which consists in subjecting a mixture of raw materials containing ironVmanganese and the desired alloying elements in combined forms to a melting process in a basic open hearth furnace, said melting process` comprises two stages during the first of which the manganese is oxidized and transferred into the slag, whereas in the second stage' `consists in subjecting a mixture of raw materials containing iron, manganese and the desired alloying elements in combined forms to a melting process in a basic open hearth furnace said melting process comprises two stages during the first of which the manganese is oxidized and transferred into the slag whereupon the temperature is raised until in the second stage a continuous reduction of the manganese oxide into the steel bath is effected and the compounds of the alloying elements are simultaneously reduced from the slag and transferred into the bath in their metallic form.

3. A process of producing an alloyed steel which consists in subjecting a mixture of raw materials containing iron, manganese and the desired a1- loying elements in combined forms to a melting process in a basic open hearth furnace said melting process comprises two stages during the first of which the manganese is oxidized and transferred into the slag, whereupon the temperature is raised and basic materials are added until ln the second stage a continuous reduction of the manganese oxide into the steel bath is effected and the compounds of the alloying elements are simultaneously reduced from the slag and transferred into the bath in their metallic form.

4. A process of producing an alloyed steel which consis'ts in subjecting a mixture of raw materials containing iron, manganese and the desired alloying elements in combined forms to a melting process in a basic open hearth furnace, said melting process comprises two stages during the first of which the manganese is oxidized and transferred into the slag, whereupon the temperature is raised and lime is added until in the second stage a continuous reduction of the manganese oxide into the steel bath is effected and the compounds of the alloying elements are simultaneously reduced from the slag and transferred into the bath in their metallic form.

5. A process of producing an alloyed steel which consists in subjecting a mixture of raw materials containing iron, manganese and the desired alloying elements in combined forms to a melting process in a basic open hearth furnace, said melting process comprises two stages during the first of which the manganese is oxidized and transferred into the slag, whereas in the second stage a continuous reduction of the manganese oxide into the steel bath is effected and the compounds of the alloying elements are simultaneously reduced from the slag and transferred into the bath in their metallic form and finishing the process while avoiding the deoxidation of the steel by an addition of manganese.

l PAUL'Krm. 

